It's the first time I'm hearing about such an issue. An obvious first question is: do you hear sound from other applications?

next, here are a set of tests to perform:

1) run the demo at: http://highc.org/samples/demo.htmldoes you hear the sounds?

2) open HighC, then open the Tools > Messages... window. Then, open a sample (such as waves), and play it. Do you hear something? Does the message window gets filled with text? If some error messages appear, please copy/paste and post them here: they will let me understand what's going on.

Aside from that, I'm pretty sure your soundcard is not the one causing the problem. Perhaps the default Java Virtual Machine is. Can you configure your system to use Java 5 instead of the default Java 1.4 (for this, go to /Applications/Utilities/Java/Java Preferences, and set your Java runtime to 1.5...)

hmm, thanks for the fast response but afraid it's negative on everything. I hear sound from other apps, don't hear the demo, and already had Java set to 5. Tried switching to 1.4.2 just to check, but then HighC didn't even open. The only message I got wasSystem calibrated for 62.7 oscillators in realtime. (0.51s)

- does this applet work: http://www.htwm.de/vannacke/dfilter/index2.html(it opens in an external window). If it doesn't, there is an issue between your Java installation and your system. If it does, then the issue is in HighC.

- open a sample (waves), press "Play", Do you see a vertical grey bar, then a black bar showing a progress over the score?

so now, almost 2 years later, I decided to reformat my Macbook and reinstall everything, and somehow High C works now. Maybe something with Java got messed up the way I installed it before. Same OS, I'm using an Echo Audiofire 4 now, but it definitely wasn't working until I reformatted.